Microtubule assembly and shrinking

Elongating filaments are straight, whereas shrinking filaments have curved or frayed ends. MT assembly is favoured when microtubule is straight. Hydrolysis of b- tubulin bound GTP to GDP causes a conformational change in the a-,b- tubulin dimer which tenses the MT lattice. The protofilaments splay outwards when depolymerising but are prevented from doing so when the microtubule is polymerising by the presence of the GFP-tubulin cap. CAP dissociation promoted explosive depolymerisation. Microtubule associated proteins (MAPs) and some motors shift the equilibrium by promoting either assembly or disassembly.